package com.itheima.a02myhashmap;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class A01_HashMapDemo1 {
    public static void main(String[] args) {
         /*
        需求：创建一个HashMap集合，键是学生对象(Student)，值是籍贯(String)。
        存储三个键值对元素，并遍历
        要求：同姓名，同年龄认为是同一个学生

        核心点：
            HashMap的键位置如果存储的是自定义对象，需要重写hashCode和equals方法。
       */

        //1.获取到学生对象
        Student s1 = new Student("zhangsan", 23);
        Student s2 = new Student("lisi", 24);
        Student s3 = new Student("wangwu", 25);
        Student s4 = new Student("wangwu", 25);

        //2.创建HashMap集合对象
        HashMap<Student, String> hm = new HashMap<>();

        //3.添加元素
        hm.put(s1, "江苏");
        hm.put(s2, "浙江");
        hm.put(s3, "福建");
        hm.put(s4, "山东");

        //4.遍历集合
        //键值对
        Set<Map.Entry<Student, String>> entries = hm.entrySet();
        for (Map.Entry<Student, String> entry : entries) {
            Student key = entry.getKey();
            String value = entry.getValue();
            System.out.println(key + " = " + value);
        }

        System.out.println("-------------------------------");

        //键找值
        Set<Student> keys = hm.keySet();
        for (Student key : keys) {
            String value = hm.get(key);
            System.out.println(key + " = " + value);
        }

        System.out.println("-------------------------------");

        //Lambda表达式
        hm.forEach(( key,  value) -> System.out.println(key + " = " + value));
    }
}
